The present invention relates to a process for the control of a transmission with several gears for an engine-driven vehicle provided with a control system for the transmission, a clutch to connect the engine to the transmission, an operating unit for the selection of a desired gear and means for detecting a rotational speed of the transmission input.
A process of this type is disclosed, for example, in WO97/44210 (U.S. Pat. No. 5,741,202).
The known process is used to control a manually switchable, non-synchronized vehicle transmission of conventional construction, with a plurality of gears, and which is operated in part automatically by means of a control system, which shall be hereinafter referred to as a transmission control system. The automation is with regard to the mechanical movements required for changing gears, which are carried out by an electrical/pneumatic adjusting device as a result of triggering signals is not connected mechanically to the transmission as in conventional transmissions, but rather transmits corresponding signals to the transmission control system when it is actuated.
The transmission is connected to the driving engine of the vehicle via a clutch operable by the driver in such manner that it can be uncoupled. In the known process, the transmission control system effects automated switching from the currently used gear into the gear selected by the driver, depending upon an actuation of the operating unit by the driver. At the same time, the transmission control system transmits suitable control signals to an engine control device in addition to the trigger signals transmitted to the electric/pneumatic adjusting device. These control signals control the engine performance in such manner that the clutch need not be opened for a gear change. As a result the driver is relieved from having to actuate the clutch during a change of gear during travel.
When the transmission is in neutral position, i.e. when no gear is engaged and the vehicle is stopped or coasts at a relatively low speed, the transmission input rotates at the relatively high speed of the drive engine with an engaged clutch, while the transmission output is stopped, or rotates at a relatively low speed. In such event, the transmission control system cannot achieve any synchronization of the toothed wheels of the transmission, and therefore, no gear can be engaged. Engaging a gear in such situation is only possible when the clutch is disengaged.
After disengaging the clutch, the speed of the transmission input is reduced rather quickly, until it comes to a stop. When necessary, this reduction in speed can be further assisted by actuation of a brake acting upon the transmission input. In such case, a problem may occur by which a gear selection is prevented by a tooth-on-tooth position of the transmission claws. Such a condition cannot be easily recognized by the driver when utilizing a transmission control system of the aforementioned type. In conventional transmissions in which a gear shift lever is mechanically connected to the transmission, the driver of the vehicle would be able to recognize haptically whether a tooth-on-tooth position has occurred by sensing a certain degree of resistance as he actuates the gear shift lever. In such event, it would then be necessary to engage the clutch to remedy the situation.
In a transmission control system of the presently described type to which the invention is directed, no haptic message is transmitted to the driver through a gear shift lever.
It is therefore the object of the present invention to propose a process for the control of a non-synchronized transmission which would make it possible to easily and reliably engage a selected gear, in particular while the vehicle is stopped.